On 18/02/14 15:21, Phi wrote:
I paid about £180 for an HP35 in 1973, this calculator used reverse
polish notation (no equals key).
That seems cheap for an HP at the time. As I recall, that was the launch
price of the Sinclair, although it soon dropped.

The Sinclair was also RPN, as were the early Texas calculators I think.
Sinclair lacked the "Enter" button, using the + key its place.

For the 'everyday' user, RPN was not popular and calculators offering,
almost, algebraic, entry became more popular. I think the first
calculator to offer true algebraic entry (ie following BODMAS/BIDMAS
convention) was Texas. Even today some cheap calculators don't follow
the convention. One of the many things I warn pupils of when I teach
calculator use.